Study: Climate Models Overestimated Global Warming For The Last 55 Years

Climate models relied upon by scientists and governments may be greatly overstating the warming that has occurred since the late 1950s, argues a paper analyzing the discrepancies between modeled and observed temperatures.

According to McKitrick, all climate models predict that rising carbon dioxide levels will cause rapid warming in the troposphere over the tropics. But that’s not what has happened, as neither satellites nor weather balloons have detected much warming in the tropical troposphere — meaning something is likely wrong with the models.

It’s not only that the models overestimate the amount of warming in the tropical troposphere, it’s that the models misrepresent the warming by making it look like a “smooth upward trend.” But McKitrick says that observations show all the warming occurred in a “single step-change in the late 1970s coinciding with a known event (the Pacific Climate Shift), and identify no significant trend before or after.”

“In my opinion the simplest and most likely interpretation of these results is that climate models, on average, fail to replicate whatever process yielded the step-change in the late 1970s and they significantly overstate the overall atmospheric response to rising CO2 levels,” McKitrick said.

What this means is that tropical tropospheric temperatures were relatively flat before the late 1970s. Then, around 1977, temperatures jumped up slightly in a phenomenon called the Pacific Climate Shift. But after the climate shift, temperatures flattened out once again, showing little to no warming trend.

The absence of warming is another area of climate science that sparks debate. In fact, McKitrick’s study is not the first to point out the inconsistencies between modeled and observed temperatures. In 2006, the U.S. Climate Change Science Program report found there was a “potentially serious inconsistency” in the modeling of tropospheric warming.

Other papers came to a similar conclusion, but were rejected by some in the climate science community. A 2011 paper by American and British government scientists said that there “is no reasonable evidence of a fundamental disagreement between tropospheric temperature trends from models and observations when uncertainties in both are treated comprehensively.”

But climate scientists continue to debate the huge differences between observed and modeled tropospheric temperatures and what it means for predicting global warming.

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